
\(\eta \)  is defined by (REF ), \(k_j, c_j,d_j\in \mathbb {C}\) .
2SS has been investigated in [1]} where the solution is expressed
in terms of determinants of Cauchy matrix type.
We can conduct similar analysis on two-soliton interaction and present same results as in [1]}.
For completeness of this paper, in the following we skip details but only sketch main results.
